The present invention relates, as indicated, to a novel process for the production of aromatic polyamides and mixed aromatic-aliphatic polyamides. The term "aromatic polyamides" as used herein will be understood as generic to mixed aromatic-aliphatic polyamides. Relatively few such polyamides have been produced to this point, this field of investigation being quite new. One notable product, however, is poly(p-benzamide), also once known as "Fiber B" and produced by DuPont Company. This material has been found useful in the production of tire cord materials. The present process enables the production of aromatic polyamide materials very similar to poly(parabenzamide) and related types of aromatic polyamides.
Basically, the present process depends upon the thermal polymerization of certain amidine materials and derivatives thereof. The rearrangement which is involved in the polymerization step appears to be unknown. These polymerizations are characterized by the formation of a low molecular weight alkyl amide such as formamide or acetamide which is easily removed from the reaction mass, leaving the aromatic polyamide as a residue.
Prior art relating to the monomers and condensation products thereof appears to be quite limited. U.S. Pat. No. 3,133,078 to Steiger contemplates the production of certain oxazol formamidines of primary amines which are pharmaceutically useful. Bredereck et al. Chem. Ber, 97(12), 3397-3406 (1964), teaches the preparation of N,N-1,4-phenylene bis-(N',N'-dimethyl formamidine) hydrochloride and the free base thereof. This material is produced from phosphorus oxychloride and dimethyl formamide in benzene. French Pat. No. 1,444,228 dated July 1, 1966, teaches the preparation of a bis-formamidine derived from an aliphatic diamine and reacted with an aliphatic diisocyanate to yield a polymer which is filmforming. The reaction is conducted in the presence of water.
Cefelin et al., Collection of Czech. Chemical Comm. 25 2522-9 (1960) discloses a reaction between N,N'-bis[2-(1-azacycloheptenyl)]-p-phenylene diamine with terephthalic acid for a period of 2 hours at 260.degree.C. This is said to yield a polyamide which is light brown and melts at a temperature more than 400.degree.C.
The present invention is based upon the discovery that various aromatic amidine and amidine derivatives may be thermally polymerized to produce a whole range of aromatic polyamides. These polymers may be used to form filaments and yarns by the application of known techniques. The resultant filaments, as monofilaments or as yarns, may in accordance with known practice be used in the preparation of reinforcing elements for elastomeric materials, e.g. tire cord materials.
Definitions of Symbols Used Herein:
Ar = aromatic ring, e.g. phenylene, naphthylene. PA0 R = alkyl and substituted alkyl, aryl and substituted aryl, alkyl and/or aryl substituted by halogen (chlorine, bromine, fluorine, iodine), alkoxy, aryloxy, carboalkoxy, carboaryloxy, carboxamide, N-substituted carboxamide, carboxamido, N-substituted carboxamido, sulfonamide, N-substituted sulfonamido, cyano, cycloalkyl, heterocycloalkyl, heteroaryl, and substituted cycloalkyl, substituted heterocycloalkyl, substituted heteroaryl, the substituents being selected from different R groups as defined. PA0 R.sub.1 = hydrogen, or lower alkyl, e.g. methyl, ethyl, n-propyl, isopropyl. PA0 R.sub.2 = lower alkyl, e.g. methyl or H. PA0 R.sub.3 = lower alkyl, e.g. methyl or H. PA0 X = carbon. PA0 X' = carbon. PA0 Y = a covalent bond, or a divalent radical, e.g. alkylene, cycloalkylene, branched alkylene, halogen-substituted alkylene, halogen-substituted branched alkylene, halogen-substituted cycloalkylene, alkoxy-substituted alkylene, alkoxy-substituted branched alkylene, thioalkoxy-substituted alkylene, thioalkoxy-substituted branched alkylene, arylene, alkyl arylene, alkoxy arylene, thioalkoxy arylene, ##EQU1## heteroarylene, heterocycloalkylene, etc. m = an integer from 1 to 4. PA0 n = an integer from 1 to 4. PA0 (R) = hydrogen, or R. PA0 x = an integer to an inherent viscosity in the range of 0.2 to 7 as measured in concentrated H.sub.2 SO.sub.4 at 0.5% concentration at 25.degree.C.